Traditionally, adhesive materials comprise wet glue-like substances that are sticky to the touch and tend to leave a residue when removed. Additionally, these substances tend to be limited in use. For example, their efficacy may be substantially reduced in water, in vacuums, on certain plastics, on certain fabrics, etc. A hook-and-loop type fastener may overcome some of the deficiencies noted in traditional glue-like adhesive materials; however, a dual surface (i.e., two separate surfaces designed to engage one another) is required to enable such a fastener. A magnet may also overcome some of the deficiencies noted in traditional glue-like adhesive materials; however, magnets are limited to ferrous materials. Such difficulties are particularly noted when fastening a disposable absorbent article.
Geckos have a remarkable ability to climb and adhere to surfaces of many different kinds, including smooth hydrophobic and hydrophilic surfaces. Examination of gecko feet reveals that numerous minute hairs, called setae, are the agents of this adhesion. These gecko setae, with diameters in the range of 0.2 to 0.5 microns, are adapted to conform well to the microscopic structure of whatever surface the geckos wish to traverse. As the setae contact the surface, an attraction between the setae and the opposing surface can allow the setae to adhere with forces in the order of 100 nanoNewtons (nN) each. At the same time, the setae can be readily separated from an opposing surface by what is surmised to be the curling of the gecko's toes to peel the setae away. The movement of the gecko allows the setae to repeatedly be adhered to and removed from opposing surfaces. Principles of gecko adhesion are discussed in more detail by Kelly Autumn et al., “Evidence for van der Waals Adhesion in Gecko Setae,” Proceedings of the National Academy of Sciences of the United States of America, Vol. 99, No. 19, pp. 12,252-12,256 (Sep. 17, 2002), and by Robert J. Full et al., “Adhesive Microstructure and Method of Forming the Same,” WO 01/49776, published Jul. 12, 2001, both of which are incorporated by reference in their entireties. Principles for construction of biomimetic gecko-like adhesives are also disclosed in U.S. patent application Ser. No. 10/197,763, filed Jul. 18, 2002 by Fearing et al. and in U.S. patent application Ser. No. 10/039,574, filed Jan. 2, 2002 by Autumn et al., both of which are herein incorporated by reference.
It is therefore desirable to obtain a fastening means for a disposable absorbent article that is dry in nature. It is further desirable that such a fastener would be sticky only when desired. It is further desirable that such a fastener would not leave a residue when removed. It is further desirable that such a fastener would stick to most surfaces. It is still further desirable that such a fastener would require only a single surface for adhesion.